It has become possible to transfer nucleic acids from a wide variety of organisms to plants utilizing recombinant DNA technology. For example, this technology has provided a mechanism to improve various agronomic properties including plant resistance to drought, temperature extremes, pests, diseases, and herbicides. However, the lack of efficient and reproducible transformation and regeneration from plant cell culture systems for many agriculturally significant crops has been a substantial barrier to the application of genetic engineering technology to plants. Moreover, there is a potential for the occurrence of somaclonal variation when plants are regenerated adventitiously in vitro. Somaclonal variation is genetic variability commonly observed in plants that originate from, e.g., a callus intermediate. This genetic variability is typically undesirable as the maintenance of the genetic integrity of transformed plants is generally an objective.